Takeshi Urade

Fabrication of a magnesium alloy with excellent ductility for biodegradable clips.

UNLABELLED To develop a biodegradable clip, the equivalent plastic strain distribution during occlusion was evaluated by the finite element analysis (FEA) using the material data of pure Mg. Since the FEA suggested that a maximum plastic strain of 0.40 is required to allow the Mg clips, the alloying of magnesium with essential elements and the control of microstructure by hot extrusion and annealing were conducted. Mechanical characterization revealed that the Mg-Zn-Ca alloy obtained by double extrusion followed by annealing at 673K for 2h possessed a fracture strain over 0.40. The biocompatibility of the alloy was confirmed here by investigating its degradation behavior and the response of extraperitoneal tissue around the Mg-Zn-Ca alloy. Small gas cavity due to degradation was observed following implantation of the developed Mg-Zn-Ca clip by in vivo micro-CT. Histological analysis, minimal observed inflammation, and an only small decrease in the volume of the implanted Mg-Zn-Ca clip confirmed its excellent biocompatibility. FEA using the material data for ductile Mg-Zn-Ca also showed that the clip could occlude the simulated vessel without fracture. In addition, the Mg-Zn-Ca alloy clip successfully occluded the renal vein. Microstructural observations using electron backscattering diffraction confirmed that dynamic recovery occurred during the later stage of plastic deformation of the ductile Mg-Zn-Ca alloy. These results suggest that the developed Mg-Zn-Ca alloy is a suitable material for biodegradable clips. STATEMENT OF SIGNIFICANCE Since conventional magnesium alloys have not exhibited significant ductility for applying the occlusion of vessels, the alloying of magnesium with essential elements and the control of microstructure by hot extrusion and annealing were conducted. Mechanical characterization revealed that the Mg-Zn-Ca alloy obtained by double extrusion followed by annealing at 673K for 2h possessed a fracture strain over 0.40. The biocompatibility of the alloy was confirmed by investigating its degradation behavior and the response of extraperitoneal tissue around the Mg-Zn-Ca alloy. Finite element analysis using the material data for the ductile Mg-Zn-Ca alloy also showed that the clip could occlude the simulated vessel without fracture. In addition, the Mg-Zn-Ca alloy clip successfully occluded the renal vein. Microstructural observations using electron backscattering diffraction confirmed that dynamic recovery occurred during the later stage of plastic deformation of the ductile Mg-Zn-Ca alloy.

Contrast-Enhanced Intraoperative Ultrasonic Cholangiography for Real-Time Biliary Navigation in Hepatobiliary Surgery

Recent progress in medical technology, perioperative management, and surgical technique has contributed greatly to the safety of hepatobiliary surgery. In particular, imaging techniques, including intraoperative imaging, have played a major role in advancing the success of these operations. Precise assessment of biliary anatomy before and during surgery reduces biliary complications. More than 42% of the population is reported to have anatomical variations of the biliary tree. If a biliary anatomical variation is suspected before surgery, confirmatory intraoperative cholangiography (IOC) is recommended. Using radiography and iodinated contrast medium, IOC was first reported by Mirizzi in 1937 and has been widely used to define the biliary tree in surgery for benign and malignant diseases. However, radiographic IOC has several drawbacks; it exposes patients and medical staff to radiation, it requires a large C-arm machine for fluoroscopy and an attendant to operate it, and it requires special techniques to generate 3-dimensional (3D) images. Intraoperative ultrasonography, specifically, contrast-enhanced intraoperative ultrasonic cholangiography (CE-IOUSC), can address these issues. Intraoperative ultrasonography has become an essential tool for the identification of intrahepatic vessels, tumor location, and definition of surgical margins for safe and effective hepatic surgery. Its diagnostic accuracy has been enhanced by the introduction of intravascular ultrasound contrast agents. However, it is still limited in visualization of nondilated bile ducts.

Development of a new biodegradable operative clip made of a magnesium alloy: Evaluation of its safety and tolerability for canine cholecystectomy

Background: Operative clips used to ligate vessels in abdominal operation usually are made of titanium. They remain in the body permanently and form metallic artifacts in computed tomography images, which impair accurate diagnosis. Although biodegradable magnesium instruments have been developed in other fields, the physical properties necessary for operative clips differ from those of other instruments. We developed a biodegradable magnesium‐zinc‐calcium alloy clip with good biologic compatibility and enough clamping capability as an operative clip. In this study, we verified the safety and tolerability of this clip for use in canine cholecystectomy. Methods: Nine female beagles were used. We performed cholecystectomy and ligated the cystic duct by magnesium alloy or titanium clips. The chronologic change of clips and artifact formation were compared at 1, 4, 12, 18, and 24 weeks postoperative by computed tomography. The animals were killed at the end of the observation period, and the clips were removed to evaluate their biodegradability. We also evaluated their effect on the living body by blood biochemistry data. Results: The magnesium alloy clip formed much fewer artifacts than the titanium clip, and it was almost absorbed at 6 months postoperative. There were no postoperative complications and no elevation of constituent elements such as magnesium, calcium, and zinc during the observation period in both groups. Conclusion: The novel magnesium alloy clip demonstrated sufficient sealing capability for the cystic duct and proper biodegradability in canine models. The magnesium alloy clip revealed much fewer metallic artifacts in CT than the conventional titanium clip.

Contrast-enhanced intraoperative ultrasonic cholangiography in living donor hepatectomy.

Radiographic intraoperative cholangiography (R-IOC) has been widely used to reduce the incidence of biliary complications in living donor hepatectomy (LDH), but it has some drawbacks including radiation exposure and difficulty with handling a C-arm machine for generating 3D images and delineating thin caudate branches. We recently developed contrast-enhanced intraoperative ultrasonic cholangiography (CE-IOUSC) as a tool for biliary navigation in hepatobiliary surgery. We compared the feasibility and usefulness of CE-IOUSC and R-IOC in LDH for visualizing the biliary system and facilitating bile duct division. Seven consecutive patients who underwent LDH using CE-IOUSC and R-IOC between January 2013 and December 2015 in our institute were enrolled. The detectability of each hepatic duct, biliary configuration types, and caudate branches around the cutting point of the hepatic duct was compared. The detectability of each hepatic duct and biliary configuration types was 100%, 100%, 86%, and 100% in drip infusion cholangiography-computed tomography, R-IOC, and 3D/2D CE-IOUSC, respectively. 2D CE-IOUSC could detect caudate branches draining into the cutting side of the hepatic duct, similar to R-IOC (p<0.01). In conclusion, CE-IOUSC is a novel intraoperative cholangiography technique for LDH, it provides excellent visualization of the biliary tree. It facilitates identification of the biliary system, guidance for bile duct division, and confirmation of the remnant biliary system. This article is protected by copyright. All rights reserved.